Generation of high-power electron beams in magnetron guns with secondary-emission cathodes

High-power electrons beams generated in a single injection magnetron gun with secondary-emission cathodes and in a set of such guns are studied. Hollow electron beams of current 50–100 A, electron energy 30–100 kV, and peak power 1–5 MW are obtained. The beams can be used as electron sources in accelerators and ordinary and multibeam high-power microwave devices.     

Computational modelling of amperometric biosensors in the case of substrate and product inhibition

In this paper the response of an amperometric biosensor at mixed enzyme kinetics and diffusion limitations is modelled in the case of the substrate and the product inhibition. The model is based on non-stationary reaction–diffusion equations containing a non-linear term related to non-Michaelis–Menten kinetics of an enzymatic reaction. A numerical simulation was carried out using a finite difference technique. The complex enzyme kinetics produced different calibration curves for the response at the transition and the steady-state. The biosensor operation is analysed with a special emphasis to the conditions at which the biosensor response change shows a maximal value. The dependence of the biosensor sensitivity on the biosensor configuration is also investigated. Results of the simulation are compared with known analytical results and with previously conducted researches on the biosensors.     

Carrier envelope phase stabilization of a Yb:KGW laser amplifier

In this paper we report on the active stabilization of the carrier envelope phase (CEP) of a Yb:KGW chirped pulse amplifier laser system seeded by a Yb-doped solid-state Kerr-lens mode-locked oscillator. The regenerative amplifier delivers 180 fs CEP stable pulses of 30 μJ-1 mJ energy at a repetition rate tunable from 1 to 200 kHz. The bandwidth of the feedback loop was extended by a factor of 5 using a specially designed high-pass filter, which resulted in a dramatic decrease of CEP jitter below 0.45 rad after the amplifier.     

Ionic liquids: Promising green solvents for lignocellulosic biomass utilization

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Generation of high-power electron beams in magnetron guns with cold secondary-emission cathodes

The generation of powerful electron beams in a single magnetron gun and in a set of magnetron guns with cold secondary-emission cathodes is studied. The possibility of generating tubular electron beams of current 50–100 A, particle energy 30–100 kV, and pulse power 1–5 MW is shown. Such beams can be used as electron sources in the technology of accelerators, as well as in ordinary and multibeam high-power microwave devices.     

Rapid formation of an electron beam in a magnetron gun with a secondary-emission metallic cathode

The initial stage of forming the electron sheath and electron beam generation in magnetron guns for the case when the secondary emission process is triggered by nanosecond pulses is considered. In the guns with small transverse sizes, tubular electron beams with an outer diameter of 4–6 mm and a current of 1–2 A are produced at a cathode voltage of 5–10 kV. It is shown that the formation of the electron cloud and beam current pulse front for a time of ≥2 ns is a possibility.     

Subtilisin-catalyzed resolution of N-acyl arylsulfinamides

We report the first biocatalytic route to sulfinamides (R-S(O)-NH2), whose sulfur stereocenter makes them important chiral auxiliaries for the asymmetric synthesis of amines. Subtilisin E did not catalyze hydrolysis of N-acetyl or N-butanoyl arylsulfinamides, but did catalyze a highly enantioselective (E > 150 favoring the (R)-enantiomer) hydrolysis of N-chloroacetyl and N-dihydrocinnamoyl arylsulfinamides. Gram-scale resolutions using subtilisin E overexpressed in Bacillus subtilis yielded, after recrystallization, three synthetically useful auxiliaries: (R)-p-toluenesulfinamide (42% yield, 95% ee), (R)-p-chlorobenzenesulfinamide (30% yield, 97% ee), and (R)-2,4,6-trimethylbenzenesulfinamide (30% yield, 99% ee). Molecular modeling suggests that the N-chloroacetyl and N-dihydrocinnamoyl groups mimic a phenylalanine moiety and thus bind the sulfinamide to the active site. Molecular modeling further suggests that enantioselectivity stems from a favorable hydrophobic interaction between the aryl group of the fast-reacting (R)-arylsulfinamide and the S1' leaving group pocket in subtilisin E.     

Investigations of electron beam characteristics using an accelerator based on a magnetron gun with a secondary-emission cathode

The reliability and service life of accelerating installations are substantially determined by the lifetime of electron sources. The accelerator under consideration has a magnetron gun with a channel-free cold secondary-emission cathode in crossed fields as an electron source [1, 2]. In the present work, the data of the electron beam parameters obtained in the accelerator based on the magnetron gun with a secondary-emission cathode are given, and possible secondary uses are suggested. The text was submitted by the authors in English.     

Terephthalic Acid Copolyesters Containing Tetramethylcyclobutanediol for High-Performance Plastics

There is a need for high-performance applications for terephthalic acid (TPA) polyesters with high heat resistance, impact toughness, and optical clarity. Bisphenol A (BPA) based polycarbonates and polyarylates have such properties, but BPA is an endocrine disruptor. Therefore, new TPA polyesters that are less hazardous to health and the environment are becoming popular. Tetramethylcyclobutanediol (TMCD) is a difunctional monomer that can be polymerized with TPA and other diols to yield copolyesters with superior properties to conventional TPA polyesters. It has a cyclobutyl ring that makes it more rigid than cyclohexanedimethanol (CHDM) and EG. Thus, TMCD containing TPA copolyesters can have high heat resistance and impact strength. TPA can be made from abundantly available upcycled polyethylene terephthalate (PET). Therefore, this review discusses the synthesis of monomers and copolyesters, the impact of diol composition on material properties, molecular weight, effects of photodegradation, health safety, and substitution of cyclobutane diols for future polyesters.     

Enantiocomplementary enzymes: classification, molecular basis for their enantiopreference, and prospects for mirror-image biotransformations

One often-cited weakness of biocatalysis is the lack of mirror-image enzymes for the formation of either enantiomer of a product in asymmetric synthesis. Enantiocomplementary enzymes exist as the solution to this problem in nature. These enzyme pairs, which catalyze the same reaction but favor opposite enantiomers, are not mirror-image molecules; however, they contain active sites that are functionally mirror images of one another. To create mirror-image active sites, nature can change the location of the binding site and/or the location of key catalytic groups. In this Minireview, X-ray crystal structures of enantiocomplementary enzymes are surveyed and classified into four groups according to how the mirror-image active sites are formed.